Middlebury astronomer uncovers quasar mystery

What was happening in the universe 12 billion years ago? The universe was smaller and galaxies collided with each other. Middlebury College’s Eilat Glikman looked at dusty quasar surroundings. (Credits: NASA/ESA)

A Middlebury College researcher is using the NASA-ESA Hubble Space Telescope’s infrared vision to uncover the mysterious early formative years of quasars, the brightest objects in the universe.

“The Hubble observations are definitely telling us that the peak of quasar activity in the early universe is driven by galaxies colliding and then merging together,” said Dr. Eilat Glikman, an assistant professor and research scientist at Middlebury College. “We are seeing the quasars in their teenage years, when they are growing quickly and all messed up.”

Discovered in the 1960s, a quasar, which is a word contraction of “quasi-stellar object,” pours out the light of as much as one trillion stars from a region of space smaller than our solar system. It took more than two decades of research to come to the conclusion that the source of the light is a gusher of energy coming from supermassive black holes inside the cores of very distant galaxies.

The lingering question has been what turns these brilliant beacons on? Now Hubble has provided the best solution.

“We’ve been trying to understand why galaxies start feeding their central black holes, and galaxy collisions are one leading hypothesis. These observations show that the brightest quasars in the universe really do live in merging galaxies,” said co-investigator Kevin Schawinski of the Swiss Federal Institute of Technology Zurich.

Glikman came up with a clever way to use Hubble’s sensitivity at near-infrared wavelengths of light to see the host galaxies by aiming at quasars that are heavily shrouded in dust. The dust dims the quasar’s visible light so that the underlying galaxy can be seen.

Glikman, who received her PhD in astronomy at Columbia University in 2006, looked for candidate “dust-reddened quasars” in several ground-based infrared and radio sky surveys.

Active galaxies in this early phase of evolution are predicted to glow brightly across the entire electromagnetic spectrum, making them detectable in radio and near-infrared wavelengths that are not as easily obscured as other radiation.

She then used Hubble’s Wide Field Camera 3 to take a detailed look at the best candidate targets. Glikman looked at the dust-reddened light of 11 ultra-bright quasars that exist at the peak of the universe’s star-formation era, which was 12 billion years ago. The infrared capability of Hubble’s Wide Field Camera 3 was able to probe deep into the birth of this quasar era.

Glikman’s technical paper was published in the Astrophysical Journal recently.